Content area
Full Text
REVIEW
Silicone Emulsions and Surfactants
Anthony J. OLenick, Jr.
Siltech LLC, Dacula, Georgia 30019
ABSTRACT: This review is intended to supply the practicing chemist with a working knowledge of the chemistry of silicone compounds. It has been divided into two parts, the rst dealing with basic chemistry of silicones [OLenick, A.J., JSD 2, 229 (2000)] and the second with silicone-based surfactants, specically dimethicone copolyols and their derivatives. This is the second part of the review. Although silicone compounds have been known for over 50 yr, the chemistry of these materials remains elusive to the average formulating chemist. This is indeed unfortunate, since the chemistry of the silicon atom and silicone compounds is every bit as wide in scope and rich in content as the chemistry of the carbon atom and the surfactant chemistry upon which it is based. This article will deal with the various methods of delivering silicone from aqueous systems. The two approaches are (i) to make emulsions that contain silicone oil and a surfactant pair and the (ii) to make modify the molecule chemically to make the product more water-compatible. Both approaches find applications in a variety of industrial applications, with different challenges to the formulator.
Paper no. S1176 in JSD 3, 387393 (July 2000).
KEY WORDS: Dimethicone, dimethicone copolyol, emulsions, 3D HLB, polysiloxane, silicon, silicone, silicone esters, surfactants.
Because most silicone compounds are water-insoluble (1), they are delivered in aqueous systems from emulsions. In many processes, emulsions are acceptable. In other processes, they complicate matters; and in some, they are completely ineffective.
EMULSIONS
Because silicone uids are water insoluble, any use of these materials in an aqueous system requires special surfactants and processing equipment. The most common processing equipment is a homogenizer, which uses mechanical energy
to break the silicone into small units. This improves the stability of the emulsion. Proper selections of the surfactant system as well as the process conditions in homogenzation are critical to making good emulsions. Poorly made emulsions will split into an oil phase and a water phase.
Silicone emulsion products generally contain the following components: (i) water, typically at least 40%, (ii) silicone, typically 55%, and (iii) a surfactant to make an emulsion. Silicone contained in an emulsion is delivered from a micelle.Since equilibrium exists...